Ferments are foods or drinks that have been transformed by microbes such as bacteria or yeast, which break down sugars and other components to create new flavors, textures, and often extra acids or gases like bubbles.

What “ferments” means

In food, ferments usually refers to:

  • Foods or beverages that have undergone fermentation, such as yogurt, kimchi, sauerkraut, kombucha, sourdough, and miso.
  • The live microbes or “cultures” themselves (for example, a sourdough starter or kombucha SCOBY) that drive the fermentation process.

In a broader science sense, fermentation is a chemical process where microorganisms break down molecules like glucose without needing oxygen, producing things like alcohol, organic acids, and carbon dioxide.

How ferments work (in simple terms)

During fermentation, microbes “eat” sugars and other nutrients in the food and convert them into:

  • Acids (like lactic acid in yogurt and sauerkraut)
  • Alcohol (like in beer and wine)
  • Gases (like carbon dioxide that makes bread rise or drinks fizzy)

This process can:

  • Change flavor (more sour, funky, complex)
  • Change texture (crunchier or softer)
  • Help preserve food by making it more acidic and less friendly to spoilage microbes.

Common examples of ferments

Some everyday ferments include:

  • Yogurt, kefir, and many cheeses
  • Sauerkraut, kimchi, pickles made by lactic acid fermentation (not just vinegar)
  • Sourdough bread
  • Kombucha, kvass, ginger beer
  • Soy products like miso, soy sauce, and tempeh

These foods often carry distinctive tangy or umami flavors because of the compounds produced during fermentation.

Why people care about ferments now

Fermented foods have become trendy again in the 2020s thanks to:

  • Interest in gut health and the microbiome (many ferments contain live “good” bacteria, though effects can vary by person and product).
  • Desire for traditional, low-tech ways to preserve food.
  • Their complex flavors that chefs and home cooks like to experiment with.

Not all ferments are equally beneficial or safe; salt levels, temperature, hygiene, and storage all matter.

Are ferments always safe?

Properly made ferments are generally safe, but:

  • Visible mold, strong off-odors, sliminess, or unusual colors are warning signs—those batches should be discarded.
  • People with certain health conditions, or who are immunocompromised, may need personalized advice before eating a lot of unpasteurized ferments.

A common rule from food safety educators is: when in doubt, throw it out.

If you’re writing a post titled “what are ferments,” do you want it more science-focused (how fermentation works) or kitchen-focused (types of fermented foods and why people make them)?